Performance.now() method returns a
DOMHighResTimeStamp, measured in milliseconds, accurate to one thousandth of a millisecond.
The value represented by
0 varies according the context:
- in shared or service workers, the epoch represents the moment the worker started.
- outside workers, or in dedicated workers created from a
Windowcontext, the epoch is the value of the
- in dedicated workers created from another worker, the epoch is set to the one of this other worker.
t = performance.now();
var t0 = performance.now(); doSomething(); var t1 = performance.now(); console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")
Date.now), the timestamps returned by
Performance.now() are not limited to one-millisecond resolution. Instead, they represent times as floating-point numbers with up to microsecond precision.
Date.now, the values returned by
Performance.now() always increase at a constant rate, independent of the system clock (which might be adjusted manually or skewed by software like NTP).
|High Resolution Time
The definition of 'Performance.now()' in that specification.
|Feature||Chrome||Firefox (Gecko)||Internet Explorer||Opera||Safari|
|Basic support||20.0 webkit
|on Web workers||33||34.0 (34.0)||?||?||?|
|Feature||Android||Chrome for Android||Firefox Mobile (Gecko)||IE Mobile||Opera Mobile||Safari Mobile|
|Basic support||4.0||25.0||15.0 (15.0)||10.0||Not supported||Not supported|
|on Web workers||?||?||34.0 (34.0)||?||?||?|
 Windows version of Chrome 20 through 33, at the time of this writing, returns
performance.now() only to millisecond precision.
- When milliseconds are not enough: performance.now() from HTML5 Rocks.